Cep E-mm is an intermediate-mass Class 0 protostellar system of luminosity 100 L\(_{\odot }\)  [1]}, [2]}, embedded in an envelope of \(35\hbox{\hspace{1.99997pt}$M_\odot $}\)  [3]}, located in the Cepheus OB3 association at a distance of \(819\pm 16\hbox{\hspace{1.99997pt}pc}\)  [4]}. Using the NOEMA interferometer, [5]} presented evidence of a protobinary system with a separation of 135 (1100 au) between component A located at \(\alpha _{J2000}\) = \(23^h 03^m 128\) , \(\delta _{J2000}\) = \(+61\hbox{\hspace{1.99997pt}$^{\rm o}$}42260\)  and component B at \(\alpha _{J2000}\) = \(23^h03^m127\) , \(\delta _{J2000}\) = \(+61\hbox{\hspace{1.99997pt}$^{\rm o}$}422485\) . While both protostars power a high-velocity jet, the outflow from component A attracted attention because of its high luminosity in the near-infrared, in particular in the H\({}_2\)  rovibrational line S(1) \(\nu \) = 1–0 at \(2.12\)  \(\mu \) m [6]}, a probe of shocked molecular gas. We will refer indistinctly to the driving protostar as "A" or "Cep E-A" in what follows.
